There was no pre-accident malfunction of the aircraft found that could have led to this occurrence. The weight of the aircraft was within limits, although it was heavy, and the engine was apparently operating normally. The weather was good and should not have been a factor. From witness descriptions and examination of the crash site, it was established that the aircraft stalled at low level shortly after take-off. Because of the low altitude at which the aircraft stalled, there was insufficient time for the aircraft to recover before it struck the ground. It could not be determined why the aircraft stalled; however, the high gross weight of the aircraft resulted in reduced aircraft climb performance, as observed by witnesses after take-off, which may have had a bearing on the stall. There was nothing found to indicate that the presence of lithium in the pilot's blood affected his ability to fly the aircraft.Analysis There was no pre-accident malfunction of the aircraft found that could have led to this occurrence. The weight of the aircraft was within limits, although it was heavy, and the engine was apparently operating normally. The weather was good and should not have been a factor. From witness descriptions and examination of the crash site, it was established that the aircraft stalled at low level shortly after take-off. Because of the low altitude at which the aircraft stalled, there was insufficient time for the aircraft to recover before it struck the ground. It could not be determined why the aircraft stalled; however, the high gross weight of the aircraft resulted in reduced aircraft climb performance, as observed by witnesses after take-off, which may have had a bearing on the stall. There was nothing found to indicate that the presence of lithium in the pilot's blood affected his ability to fly the aircraft. The high gross weight of the aircraft resulted in reduced aircraft climb performance. The aircraft stalled, for undetermined reasons, at too low an altitude to be recovered. The pilot had been prescribed the drug Lithium, which was not reported to Transport Canada.Findings The high gross weight of the aircraft resulted in reduced aircraft climb performance. The aircraft stalled, for undetermined reasons, at too low an altitude to be recovered. The pilot had been prescribed the drug Lithium, which was not reported to Transport Canada. The aircraft stalled, for undetermined reasons, at too low an altitude to be recovered.Causes and Contributing Factors The aircraft stalled, for undetermined reasons, at too low an altitude to be recovered.